1. Field of the Invention
The present invention relates to a liquid crystal display module.
2. Discussion of the Related Art
Until recently, display devices have typically used cathode-ray tubes (CRTs). Presently, many efforts and studies are being made to develop various types of flat panel displays, such as liquid crystal display (LCD) devices, plasma display panels (PDPs), field emission displays, and electro-luminescence displays (ELDs), as a substitute for CRTs. Of these flat panel displays, LCD devices have many advantages, such as high resolution, light weight, thin profile, compact size, and low voltage power supply requirements.
Generally, an LCD device includes two substrates that are spaced apart and face each other with a liquid crystal material interposed between the two substrates. The two substrates include electrodes that face each other such that a voltage applied between the electrodes induces an electric field across the liquid crystal material. Alignment of the liquid crystal molecules in the liquid crystal material changes in accordance with the intensity of the induced electric field into the direction of the induced electric field, thereby changing the light transmissivity of the LCD device. Thus, the LCD device displays images by varying the intensity of the induced electric field.
The LCD device includes a backlight unit to supply light to a liquid crystal panel. The backlight unit is categorized into an edge type and a direct type. The edge type backlight unit includes a lamp at a side of a light guide plate. The direct type backlight unit includes a plurality of lamps below the liquid crystal panel.
FIG. 1 is a cross-sectional view of an LCD module including a direct type backlight unit according to the related art.
Referring to FIG. 1, the LCD module includes a liquid crystal panel 10, a direct type backlight unit 20, a main supporter 30, a top case 40 and a bottom case 50.
The liquid crystal panel 10 includes first and second substrates 12 and 14 and a liquid crystal layer between the first and second substrates 12 and 14.
The direct type backlight unit includes a reflector 22 on the bottom case 15, a plurality of lamps 24 in parallel to one another, and a plurality of optical sheets 26. The optical sheets include a diffusion sheet, a prism sheet and a protection sheet.
Cold cathode fluorescent lamp (CCFL), an external electrode fluorescent lamp (EEFL) or an light emitting diode (LED) may be used as the lamp 24. Among these lamps, the EEFL has many advantages, such as high luminance, high efficiency, long lifetime, and low weight. When the EEFL is used as the lamp 24, the lamp 24 includes a glass tube, and both external electrodes at both ends of the glass tube. A common electrode supplies driving voltages to the external electrodes.
FIG. 2 is a cross-sectional view illustrating a portion of the LCD module according to the related art.
Referring to FIG. 2, the lamp 24 as an EEFL includes a glass tube 24a and an external electrode 24b covering an end of the glass tube 24a. The external electrode 24b is supplied with a driving voltage from a common electrode 60.
The common electrode 60 includes first and second common lines 61a and 61b and a holder 63 connected to the first and second common lines 61a and 61b. Further, the common electrode 60 includes a stopper 65 facing the end of the EEFL 24. The stopper 65 is upright and prevents the lamp 24 from moving in a length direction of the lamp 24.
A portion of the LCD module opposite to the portion of FIG. 2 has a structure symmetric to the structure of FIG. 2. Accordingly, both external electrodes 24a of the lamp 24 are supported and fixed by the holders 63 and supplied with driving voltages.
The common electrode 60 is fixed to the bottom case 50 through a screw 70. The screw 70 includes a head portion 71 and a shaft portion 73. The head portion 71 has a line shaped or cross shaped groove at the top, and the screw 70 is fastened or unfastened by a screwdriver corresponding to the groove shape. The shaft portion 73 has a spiral thread at the side.
The screw 70 is driven downward into a screw hole 80 of the common electrode 60 and the bottom case 50 to couple the common electrode 60 with the bottom case 50. The screw hole 80 has a spiral groove engaging with the spiral thread of the screw 70.
In fastening the screw 70, sometimes, the shaft 73 is not straight inserted into the screw hole 80 and is inclined into the screw hole 80 due to various causes. In this situation, the spiral thread of the screw 70 and the spiral groove of the screw hole 70 is caused to be worn away and broken down since an excessive pressure is applied in a state of not engaging the thread with the groove. Accordingly, the screw 70 is loosely coupled with the screw hole 80, and the screw 70 is unfastened and comes off due to an external pressure.
Further, even though the screw 70 is straight fastened into the screw hole 80, the LCD module swings in moving the LCD module and so on, and this sometimes causes the screw 70 to be unfastened and come off.
Such the come-off screw 70 moves in the LCD module and may damage the lamp 24. To prevent this problem, resin is coated to the thread of the shaft portion 73 or a serration is added to the head portion 71. However, these methods increase production costs.